Integrated fluid coking gasification process

ABSTRACT

A HEAVY CARBONACEOUS MATERIAL SUCH AS PETROLEUM RESIDUUM IS CONVERTED TO DISTALLATE AND GAASEOUS PRODUCTS BY AN INTERGATED PROCESS CONSISTING OF COKING SAID HEAVY CARBONACEOUS MATERIAL IN A CONVENTIONAL FLUID COKING REACTOR, AND GASIFYING THE COKE PRODUCED IN AN IMPROVED THREE ZONE GASIFYING REACTOR.

Sept. 18, 1973 G. c. LAHN 3,759,676

INTEGRATED FLUID COKING/GASIFICATION PROCESS Filed Jan. 22, 1971 +C OKER PRODUCTS FUEL GAS r i =/LH4 1 I I l I I I22 I In |2| v I l I6 I REACTOR no Q n9 :1

I20 I23 I24 AIR STEAM OR 0 T STEAM lNVENTOR GERARD C. LAHN BY MCL ATTORNEY United States Patent O 3,759,676 INTEGRATED FLUID COKING/GASIFICATION PROCESS Gerard C. Lahn, Parsippany, N.I., assignor to Esso Research and Engineering Company Filed Jan. 22, 1971, Ser. No. 108,709 Int. Cl. (110g 9/28; C10j 3/00, 3/20 US. Cl. 48-206 7 Claims ABSTRACT OF THE DISCLOSURE A heavy carbonaceous material such as petroleum residuum is converted to distillate and gaseous products by an integrated process consisting of coking said heavy carbonaceous material in a conventional fluid coking reactor, and gasifying the coke produced in an improved three zone gasifying reactor.

BACKGROUND OF THE INVENTION This invention relates to a process for producing fuel gas from coke by a novel gasifying process. More particularly the gasifying process consists of a three stage process wherein cold coke is injected into a heat transfer zone before being lifted to a gas/solids disengaging zone operated at temperatures between 900 and 1800 F., and then at least in part transferred to a gasifying zone operated at temperatures between 1600 and 2200 F.

In another embodiment this invention relates to an integrated coking-gasification process. More particularly heavy carbonaceous material such as petroleum residuum is converted to a liquid and gas petroleum distillate and coke by a conventional fluid coking reactor and the coke transferred to an improved three-stage gasifying reactor to make fuel gas.

In a conventional fluid coking process a heavy hydrocarbon fraction such as vacuum residuum is fed into a fluid coking reactor to produce a liquid and gas distillate product and coke. The coke is then preferably transferred to a separate burner reactor where a portion of the coke is burned to heat the remaining coke to a high enough temperature sufficient to supply the heat requirement needed in the coking reactor when the coke is recycled to the coking reactor.

A fluid coking process such as above has encountered several problems. First there is generally more coke produced in the coking reactor than is needed in the burner reactor. Since this coke has very little value as a byproduct disposal of this excess coke has become a problem. Another problem arises in the burning of the coke in the burner reactor. A by-product of this reaction is S which is released in the air as a pollutant. In light of the new federal and state air pollution laws this S0 emission is not acceptable.

These problems can be alleviated by adding gasifying reactors to the fluid coking reactors in order to convert the excess coke into fuel gas (H and CO) by reaction with steam. In this manner the sulfur in the coke could also be easily removed as H 8 from the fuel gas. However the necessary addition of transfer lines as well as another reactor vessel has severe economic drawbacks that make such a process undesirable.

As an alternative to the above three vessel systems a novel two stage, single vessel, heater-gasifier reactor was designed as described in application Ser. No. 880,219, now US. Pat. 3,661,543, issued May 9, 1972. This design however has created new problems which this invention now overcomes. In the design of the above pending application there exists the possibility that the heater bed would dump into the gasifier bed if any of the slide valves stuck or the gas distributor was burned through. In such a situation the two stage reactor would have to shut down, and there would be the possibility of oxygen breaking through the beds and causing an explosion. A second disadvantage was the unreliability of the gas distributor to evenly distribute the gases in the upper burner bed. This results in poor fluidization of the upper bed which in turn creates hot spots within the bed, particularly around the gas distributor, which causes destruction of the reactor, in particular the gas distributor leading to the dumping problem described above.

It is therefore an object of this invention to provide a process that economically utilizes the excess coke produced in a conventional fluid coking process, while at the same time elirnnate the S0 air pollution problem also associated with the conventional fluid coking process.

Another object of this invention is to provide a single vessel, heater-gasifier reactor process wherein the burner bed cannot unexpectedly dump in the gasifier bed.

Still another object of this invention is to provide a single vessel, heater-gasifier reactor that does not need a gas distributor apparatus between the heater bed and the gasifier bed.

A further object of this invention is to provide a single vessel, heater-gasifier reactor process which does not need high temperature slide valves or high temperature cyclones.

A still further object of this invention is to provide a process for the gasification of carbonaceous materials in which the production of fuel gas is maximized by pre heating the feed to the gasifier with the exiting hot gas.

Other objects and advantages of this invention will be apparent from the ensuing description of the invention.

SUMMARY OF THE INVENTION In one embodiment of this invention a process is disclosed wherein carbonaceous feed material, in particular coke, is gasified in a three zone reactor in a manner which maximizes the production of fuel gas by a novel method of feed preheating. More particularly the carbonaceous material is injected into an intermediate heat transfer zone where it is contacted and lifted upwardly by the hot gases produced in a lower gasifying zone until the now hotter carbonaceous material reaches the upper disengaging zone and deposits there while the now cooler gases escape the reactor vessel through low temperature cyclones.

In another embodiment of this invention an integrated fluid coking-gasifying process is disclosed wherein the coke produced in a coking reactor is injected into a three zone reactor vessel to produce fuel gas and if desired a substa ntially desulfurized hot coke product which can be injected into the fluid coking reactor to supply the heat requirements needed in that reactor, or it can be injected directly into the lower gasifying zone of the reactor vessel to produce more fuel gas, or both. More particularly the coke produced in the coking reactor is injected into an intermediate heat transfer zone where it is contacted and lifted upward by the hot gases produced in a lower gasifying zone until the new hotter coke reaches the upper disengaging zone where the cooled gas and heated coke are separated. The heated coke accumulates in the disengaging zone bed from which a portion is recycled to the coking reactor and the remainder sent to the gasifier zone where it may be converted to fuel or in part withdrawn from the reactor. The cooled gases escape the reactor through low temperature cyclones.

BRIEF DESCRIPTION OF THE DRAWING The figure schematically illustrates the preferred embodiments of the process of this invention.

3 DESCRIPTION OF THE PREFERRED EMBODIMENT As seen in the figure a heavy hydrocarbon feed is introduced into a conventional fluid coking reactor 101 by means 102. This feed could include any carbon-containing material, but for economic and availability reasons vacuum or atmospheric distillation residuum is preferred. Inert particles such as silica, alumina, zirconia, magnesia, alundum or mullite, or synthetically prepared or naturally occurring material such as pumice, clay, kieselguhr, diatomaceous earth, bauxite and the like may be used to form bed 103, but preferably bed 103 comprises coke particles, and more preferably coke particles whose diameters are between 40 and 400 microns. Bed 103 which is maintained in a fluidized state by a fiuidizing gas such as steam or if desired also by air or other oxygen-containing gas introduced by means 104. This fluidized bed 103 is maintained at a temperature between 900 and 1100 F. by coke from the disengaging zone 113 of the three zone, heater-gasifier reactor 110 introduced to the fluidized bed 103 by transfer line 105 and if desired by the burning of the residuum with the oxygen or air from means 104. Also the feed could be preheated in a furnace, not shown, before being injected into the fluid coking reactor 101.

Inside fluid coking reactor 101 the residuum is cracked to produce light liquid and gas distillate products which are removed from the reactor by cyclone means 106. A coke by-product is also produced by the reactions in bed 103 and is removed by transfer line 107 and transferred to the three zone, heater-gasifier reactor 110 by a fluidizing gas such as steam introduced into transfer line 107 by line 108. To control individual zone temperatures supplementary air or oxygen may be injected in transfer line 107 by line 109.

The coke is then injected into an intermediate heat transfer zone 111 at a rate of 5 to 60 tons/min., preferably between and 35 tons/min., where it is contacted by the hot gases produced from reactions in a lower gasifying zone 112.

The quantity and velocity of these rising hot gases must be such that the coke which enters the intermediate heat transfer zone 111 is lifted up through this zone, preferably in a draft tube means 122, so that the coke may be deposited in an upper disengaging zone 113 where it can not be dumped into the lower gasifying zone 112 because of retaining walls 121 and riser means 122 connected to reactor 110. For the process of this invention a. gas velocity above ft./sec. would be suflicient to accomplish this feat. To insure adequate heat transfer from the hot gases to the relatively cold coke a gas velocity between and 60 ft./sec. would be preferred, and a gas velocity between 40 and 50 ft./sec. most preferred. The coke deposited in the upper disengaging zone 113 by a system of baflles 114 and low temperature cyclones 115 may now be transferred by line 116 to the lower gasifying zone 112 the amount of which may be controlled by low temperature slide valve 119 or recycled back to the fluid coking reactor 101 by transfer line 117 where such transfer may be aided by steam injected into transfer line 117 by line 118.

The coke which is transferred b line 116 through low temperature slide valve 119 to the lower gasifying zone 112 is contacted by air or oxygen from line 123 and steam from line 124 so as to bring the temperature in zone 112 to between 1600" and 2200 F., preferably 1800 F. for maximum production of fuel gas. The steam and air or oxygen also serve as fluidizing gases in order to maintain the coke in the lower gasifying zone 112 in a fluidized state so as to form a fluid bed. Maintaining zone 112 as a fluid bed results in a more even distribution of heat within the zone and prevents hot spots from developing which could destroy the wall of reactor 110. The temperature is then controlled by regulating the amount of and by regulating the amount of steam introduced which results endothermically with the coke to achieve the desired balance. To maintain the temperature within the desired range an oxygen gas rate between 0.25 and 0.4 mole O /m01e C and a steam rate between 0.25 and 1.0 mole H O/mole C is desired for O /steam gasification. For air/steam gasification an air rate between 1.5 and 3.3 moles air/mole C and steam rate between 0.16 and 0.5 mole H O/mole C is desired. To maintain zone 112 within the preferred temperature of about 1800 F. the 0 "rate should be between 0.3 and 0.35 mole O /mole C and the steam rate between 0.5 and 0.8 mole H O/mole C. If air is injected into zone 112 an air rate between 2.0 and 3.0 moles air/mole C and a steam rate between 0.2 and 0.3 mole H O/mole C are used.

The gases produced, primarily H C0, C0 and S0 within zone 112 leave the zone at about the same temperature as the zone; i.e., preferably about 1800" F. These hot gases then contact the coke from the fluid coking reactor 101. Since this coke is at a temperature of onl about 950 F. there is a transfer of heat from the hot gases (1800 F.) to the cold coke (950 F.).

The amount of heat transferred can be controlled by the length of time the hot gases are in contact with the relatively cold coke. This contact time in turn is controlled by the feed rate of the cold coke into intermediate heat transfer zone 111, the gas rates of both the air or oxygen and that of the steam. According to the preferred gas rates stated previously this will provide for a contact time between 0.25 and 2.0 seconds, and preferably between 05 and 1.0 second. During this period of contact the hot gases cool down to temperatures between 1200" and 1050 F., and in the preferred conditions the gases exiting from reactor have a temperature of about 1150 F. By reducing the temperature of the gases to this level allows the use of low temperature cyclones 115 rather than expensive, unreliable high temperature cyclones, to remove the gases from reactor 110. At the same time the gases cool down, the coke is being heated to a temperature between 1200 and 1050 F. Under the preferred conditions the final temperature of the coke when it is deposited into the upper disengaging zone 113 is about 1150 F. At this temperature enough coke is available for transfer to the fluid coking reactor 101, and what coke remains may be transferred by line 116 to the lower gasifying zone 112. In order to maintain the lower gasifying zone 112 within a certain maximum level in reactor 110 a drain pipe 120 is provided that carries excess hot coke in the lower gasifying zone 112 to line 107 where the hot coke may again be introduced into the intermediate heat exchange zone. The hot coke from drain pipe 120 also provides additional heat to the coke in transfer line 107 and thereby provides further flexibility in controlling the overall process heat balance.

Having described and illustrated the invention, what is claimed as useful, novel and unobvious and desired to be secured by Letters Patent is:

1. A process for producing fuel gas from coke in a three-zone, single vessel reactor, which comprises:

(a) introducing heated coke obtained from step ((1) into a fluidized gasifying bed maintained at temperatures between 1600 and 2200 F. and positioned in the lower zone of said reactor to contact steam and an oxygen-containing gas and thereby produce a hot fuel gas;

(b) passing said hot fuel gas into an intermediate heat transfer zone positioned above and in direct communication with said lower zone and at a spaced coke is introduced into said intermediate zone at a temdistance from said gasifying bed; perature of about 950 F.

(c) introducing relatively cold coke into said inter- 5. The process of claim 1 wherein said period of time mediate zone and contacting said relatively cold coke of step (c) is between 0.25 and 2.0 seconds. with said hot fuel gas for a period of time sufiicient 5 6. The process of claim 1 wherein said heated coke is to cool the vfuel gas to a temperature below about separated from said cooled fuel gas in said disengaging 1600 F. and to heat said relatively cold coke to a zone by gravity and cyclone means. temperature above about 1050 F., at a velocity sufli- 7. The process of claim 1, wherein the velocity of said cient to raise the coke to a solids disengaging zone fuel gas contacting said coke in said intermediate zone is positioned in the upper portion of said reactor, said 10 between and feet/second. velocity being above about 25 feet/second;

(d) passing the resulting cooled fuel gas and entrained References Cited heated coke to said solids disengaging zone to sepa- UNITED STATES PATENTS rate the heated coke from the cooled fuel gas, and

2,605,215 7/1952 Coghlan 20131 X (egneggggrmg the cooled fuel gas from said disengag 15 2,591,595 4/1952 ogorzaly 48 2O6 X 2. The process of claim 1 wherein said fuel gas is g H cooled in said intermediate zone to a temperature below 0C er am about 0 F- Saxton 3. The process of claim 1 wherein said fuel gas is 20 cooled to a temperature of about 1150 F. and said rela- JOSEPH SCOVRONEK Primary Exammer tively cold coke is heated to a temperature of about 1150 US Cl. F. in said mtermediate zone.

4. The process of claim 1 wherein said relatively cold 197 208127 

